Field of the Invention
This invention relates to the graphene based electrodes and applications.
Description of the Related Art
Graphene, a single layer carbon sheet, has attracted extensive attention due to its excellent physical properties, such as quantum electronic transport, a tunable band gap, extremely high mobility and high electromechanical properties. Since the discovery of the first isolated graphene prepared by mechanical exfoliation of graphite crystals, several methods have been developed for formation of graphene, including epitaxial growth on silicon carbide and ruthenium as well as two-dimensional assembly of reduced graphene oxides and exfoliated graphene films.
Graphene films synthesized using exfoliation methods exhibit relatively poor electrical conductivity. For example, the electrical conductivity of exfoliated graphene films is reduced due to poor interlayer junction contact resistance and structural defects that are induced by mechanical stress during exfoliation and reduction processes.
In contrast, graphene films grown by epitaxial processes, such as chemical vapor deposition (CVD), possess high crystalline quality. Furthermore, CVD fabricated graphene films may be made in relatively large areas, enabling the fabrication of wafer level nanoelectronic devices. Examples of such nanoelectronic devices may include, but are not limited to, ultra-capacitors and solar cells.
Recently, large-scale patterned growth of graphene films by CVD on thin nickel layers has been reported [see, e.g., Nature, Vol. 475 (2009) 706-710; Nanoletters, Vol. 9 (2009) 30-35]. However, despite this progress, there are difficulties in achieving large-area ultra-thin graphene films having small numbers of layers (e.g., 1 layer (monolayer), 2 layers (bi-layers)). Furthermore, there are significant challenges associated with transfer of such graphene films onto a desired substrate without damaging the crystalline quality and film uniformity of the synthesized graphene.